Methanosaeta

Methanosaeta is a genus of archaea known for its role as an aceticlastic methanogen. Members are strict anaerobes that convert acetate into methane and carbon dioxide, a metabolic process that links the carbon cycle in anaerobic environments to methane production. The genus is placed in the family Methanosaetaceae and is widely found in freshwater and marine sediments, as well as in anaerobic bioreactors used for wastewater treatment and other waste digestion processes.

Physiology and metabolism emphasize acetate use. Methanosaeta species specialize in acetate as their sole carbon and energy source, typically unable to utilize other substrates for methanogenesis. They are characterized by a high affinity for acetate, allowing growth at very low acetate concentrations and enabling them to dominate in niches where acetate is scarce. The overall reaction they catalyze can be summarized as acetate plus water yielding methane plus bicarbonate, with the acetyl-CoA pathway and a CODH/ACS enzyme complex playing central roles in assimilating and converting the acetyl group to methane.

Ecology and significance are linked to biogeochemical and industrial settings. In natural sediments and wastewater treatment ecosystems, Methanosaeta often coexist with other methanogens; their competitive edge at low acetate concentrations complements the activity of organisms like Methanosarcina, which prevail at higher acetate levels. Collectively, aceticlastic methanogens such as Methanosaeta contribute substantially to methane production in anaerobic digesters and wetlands, influencing carbon flow and greenhouse gas emissions.

The genus comprises several species, including Methanosaeta concilians and Methanosaeta soehngenii, with thermophilic representatives such as Methanosaeta thermoacetophila described in the literature. As a group, they exemplify the specialization of archaea in acetate-driven methanogenesis.